<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>关键帧</title>
    <style>
        .outer{
            height:500px;
            border-bottom: 10px black solid;
            margin: 50px auto;
            overflow: hidden;/*开启BFC，避免外边距重叠*/
        }
        .outer div{
            float:left;
            width:100px;
            height:100px;
            border-radius: 50%;
            background-color: cyan;
            animation: ball 1s forwards ease-in infinite alternate;
        }
        /* .outer .box1{
            background-color: chartreuse;
        } */
        .outer .box2{
            background-color:coral;
            animation-delay: -1s;
        }
        .outer .box3{
            background-color:darkorchid;
            animation-delay: -2s;
        }
        .outer .box4{
            background-color:deeppink;
            animation-delay: -3s;
        }
        .outer .box5{
            background-color:cyan;
            animation-delay: -4s;
        }
        .outer .box6{
            background-color:deepskyblue;
            animation-delay: -5s;
        }
        .outer .box7{
            background-color:bisque;
            animation-delay: -6s;
        }
        .outer .box8{
            background-color:fuchsia;
            animation-delay: -7s;
        }
        .outer .box9{
            background-color:yellow;
            animation-delay: -8s;
        }
        
        /*创建小球下落的动画*/
        @keyframes ball{
            from{
                mergin-top:0;
            }
            /* 20%,60%,to{
                margin-top: 400px;
                animation-timing-function: ease-in;
            }
            40%{
                margin-top: 100px;
            }
            80%{
                margin-top: 400px;
            } */
            to{
                margin-top: 400px;
            }
        }

    </style>
</head>
<body>
    <div class="outer">
        <div class="box1"></div>
        <div class="box2"></div>
        <div class="box3"></div>
        <div class="box4"></div>
        <div class="box5"></div>
        <div class="box6"></div>
        <div class="box7"></div>
        <div class="box8"></div>
        <div class="box9"></div>
    </div>
    
</body>
</html>